Arachnandra Barfuss, Leme & W. Till, 2025

Leme, Elton M. C., Till, Walter, Halbritter, Heidemarie & Barfuss, Michael H. J., 2025, Arachnandra, a new monotypic genus in Tillandsioideae (Bromeliaceae) from the Atlantic Forest in Brazil, Phytotaxa 693 (1), pp. 1-32 : 24-25

Arachnandra Barfuss, Leme & W. Till , gen. nov.

Diagnosis:—This new genus differs from Alcantarea , Stigmatodon , Vriesea , and Waltillia by its unique combination of morphological characters, such as sepals lanceolate-acuminate, petals distinctly appendaged, 3.8–4.6 times longer than wide, forming an open, fan blade-like corolla, stamens radially arranged, prostrate, pollen subglobose, sulcus broad, without prominent ornamental elements, margins weakly distinct, stigma of the conduplicate-patent type, and seeds with a basal appendage distinctly longer than the inconspicuous apical appendage.

Type:— Tillandsia drepanocarpa Baker.

Description:— Plants epiphytic. Leaves thin in texture, forming water impounding rosettes; leaf sheath distinct; leaf blade narrowly lanceolate, acuminate. Inflorescence compound, with short, inconspicuous branches. Flowers diurnal, strongly fragrant, divergent to slightly secund; sepals lanceolate, acuminate, subsymmetrical; petals spathulate, 3.8– 4.6 times longer than wide, connate at the base, spreading to reflexed, forming an open, fan blade-like corolla, bearing 2 linear or narrowly lanceolate appendages; stamens shorter than the petals but exposed by the reflexed petals, radially disposed, prostrate; filaments terete, adnate to the petal tube and free above it; anthers linear, the pollen sacs with a prevailingly frontal line of dehiscence, connective area exposed and not covered by the margins of the pollen sacs; pollen subglobose, ca. 55 µm in diameter, sulcate, the sulcus broad, without ornamental elements, margins moderately distinct, with small exine elements attached; ovary almost totally superior or not more than 1/8 inferior (considering the nectary tissue), placentation totally superior; stigma of the conduplicate-patent type, white. Fruits a septicidal capsule; seeds with an umbrella-like, plumose basal coma distinctly longer than the straight, undivided inconspicuous apical appendage.

Species:— Arachnandra is a monotypic genus.

Etymology: —From classical Greek “Arachné” = spider, and “andra” = man (male), referring to the spider-like arrangement of the stamens lying on the corolla.

Distinctive characters:— Arachnandra is a member of tribe Vrieseeae , subtribe Vrieseinae , being closely related to Alcantarea , Stigmatodon , Vriesea and Waltillia . However, this new genus differs from Alcantarea by its general small size when in bloom (vs. usually large sized), flowers distinctly smaller (vs. flowers large), sepals with acuminate apex (vs. obtuse), petals 3.8–4.6 times longer than wide, spathulate (vs. 10 to 15 times longer than wide, linear or nearly so), pollen with sulcus margins moderately distinct [vs. sulcus margins sharply cut, “ Alcantarea type ”)], and seeds with a long appendage at the basal end and an inconspicuous appendage at the apical end (vs. with a short appendage at the basal end and a long appendage at the apical end).

In relation to Stigmatodon , Arachnandra can be distinguished by leaves mesomorphic (vs. semi-xeromorphic to xeromorphic), leaf blades sparsely and inconspicuously lepidote, margins not truncate (vs. densely and conspicuously lepidote, margins often truncate), inflorescence with inconspicuous lateral branches exceeded by the primary bracts (vs. simple or paniculate with large lateral branches much exceeding the primary bracts), flowers diurnal (vs. flowers nocturnal), petals much narrower, spreading to reflexed at anthesis, forming an open, fan blade-like corolla (vs. much broader, suberect and forming a campanulate corolla), petals bearing narrower, linear to lanceolate appendages (vs. bearing much broader appendages), stamens radially arranged, prostrate (vs. usually with three of them disposed in each lateral sides of the corolla), pollen globose, the sulcus broad, without ornamental exine elements [vs. ellipsoid, sulcus narrower, covered with exine elements separated from each other, forming isolated exine islands (‘insulae type’, “subtype d”)], and stigma of the conduplicate-patent type, white, densely papillate (vs. of the tubo-laciniate types I and II or convolute-blade type III, green or greenish, without papillae or sparsely papillate).

In comparison with Vriesea , it differs by flowers strongly fragrant despite diurnal (vs. odorless when diurnal or scented in night-blooming, usually bat pollinated species), sepals acuminate (vs. mostly obtuse, rounded, and emarginate, rarely acute or acuminate), petals white, spreading to reflexed at anthesis, forming an open, fan blade-like corolla (vs. yellow, often with green tips, cream, brownish-red or rarely white, usually erect in diurnal species, except for the suberect to recurved apex, forming a prevailingly tubular corolla, or corolla campanulate in night blooming species), pollen globose, sulcus broad, without ornamental exine elements [vs. ellipsoid, sulcus narrower, covered with exine elements separated from each other, forming isolated exine islands (‘insulae type’, “subtype d”)], and stigma of the conduplicate-patent type (vs. of the convolute-blade II type).

Arachnandra is also related to Waltillia , differing by leaves mesomorphic, forming water impounding rosettes (vs. semi-xeromorphic, forming non-water-impounding rosettes), flowers smaller, diurnal (vs. flowers larger, nocturnal), sepals acuminate (vs. obtuse to emarginate), petals connate at the base, white, spreading to reflexed at anthesis, forming an open, fan blade-like corolla (vs. free, pale greenish-yellow, forming a campanulate corolla), petals bearing well developed appendages (vs. unappendaged), pollen sulcus without ornamental exine elements (vs. sulcus covered by a kind of operculum of almost smooth exine elements with some perforations), stigma of the conduplicate-patent type (vs. of the convolute-blade II type), seeds with a long appendage at the basal end and an inconspicuous appendage at the apical end (vs. with a short appendage at the basal end and a long appendage at the apical end).